Chiroptera is one of the few modern mammal orders for which no fossil record has been associated with the Paleocene-Eocene Thermal Maximum that happened 55.8 million years ago. With the exception of complete skeletons from the early Middle Eocene of the Messel Formation in Germany and the late Early Eocene Green River Formation in Wyoming, all early bats are only represented by isolated elements, mainly teeth and fragmentary jaws, making the diversity and taxonomic affinities more difficult to establish. Here we revise all of the Early Eocene bats from Europe based on dental features, including digitally reconstructed teeth using micro-CT scanning technology of some complete skeletons. The diversity of European early bats is composed of the families Onychonycteridae, Icaronycteridae, Archaeonycteridae, Palaeochiropterygidae, and some of undetermined affinities. Dental features and synapomorphies of each family are characterized for the first time. The earliest bats are dated from the early Early Eocene and are all of small size with lower molars less than 1.3 mm in length. They are represented by: Eppsinycteris anglica from Abbey Wood, east London, England, an onychonycterid with reduced lower p4 and long molars; Archaeonycteris? praecursor from Silveirinha, Portugal, an archaeonycterid with long postcristid on wide lower molars; a new archaeonycterid genus and species from Meudon, North France with long trigonid and shorter postcristid on wide lower molars. These results indicate that the diversity of European Early Eocene bats is higher than previously recognized and that diversification began early in the Early Eocene.
Located in
Library
/
RBINS Staff Publications
The Cambay Formation at Vastan Mine in Gujarat yields the oldest fossil primates known from India. New age estimates suggest that the fossils date from approximately 54.5 Ma (early Ypresian), about 2 million years older than initially thought and comparable in age to early Wasatchian Wa-4 faunas from North America. The Vastan primate fauna comprises predominantly the asiadapine adapoids Marcgodinotius and Asiadapis. Two species of omomyid primates, Vastanomys gracilis and V. major, are much rarer, each known from a single dental specimen. In addition to primate dental remains, Vastan Mine has produced the best preserved early Eocene primate postcranial elements known from anywhere in the world. Here we present new limb bones, including humeri, ulnae, femora, tibiae, and a talus, from three of the recognized primate species. They include the first omomyid postcrania from India: two femora, a talus, and a potential proximal tibia. We also report additional asiadapine postcrania: a pristine femur of Marcgodinotius and the first complete tibia of Asiadapis. Five new humeri (two complete) consist of one asiadapine and four that lack specializations of either group, making allocation difficult. Two ulnae are attributed to indeterminate euprimates due to lack of adequate comparative material. The elements attributed to Vastanomys are more primitive than any other known omomyid postcrania and are only subtly different from those of asiadapines, in contrast to the more distinct postcranial bones of their middle and late Eocene relatives. The femora attributed to Vastanomys exhibit features suggestive of leaping behavior (cylindrical femoral heads, lateral condyle higher than medial, proximal position of the third trochanter), as in other omomyids. However, while the talus of Vastanomys resembles those of omomyids more than those of other primates, features such as the relatively short, medially angled neck, and oval rather than spherical head suggest that Vastanomys was not as specialized for leaping as younger omomyids. Although asiadapines have been described as close to notharctids in morphology, the relatively wider distal femur and symmetrical condyles of Marcgodinotius resemble adapids more than notharctids and may also reflect less leaping. The revised age of the fossils, together with the similarity in morphology of omomyid and asiadapine postcrania, suggests that the postcrania, like the teeth of the most primitive members of each family, are converging toward a common morphology as we approach the base of the Eocene.
Located in
Library
/
RBINS Staff Publications
